Curable fluorocopolymer formed from tetrafluoropropene

ABSTRACT

The present invention is directed to partially fluorinated copolymers and the production thereof. More specifically, the copolymers, which are preferably produced by a solution polymerization process, preferably have at least three units, the first unit selected from 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene, the second unit having a polymerized monomer selected from the vinyl esters and vinyl ethers, and the third unit having a polymerized monomer derived from a hydroxyl group-containing vinyl ether. The resulting copolymer is environmentally friendly, has favorable molecular weight characteristics, and may be shipped economically in high concentration.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. ProvisionalApplication Ser. No. 61/894,146, filed 22 Oct. 2013, the disclosure ofwhich is hereby incorporated herein by reference. The '146 ProvisionalApplication is related to U.S. application Ser. No. 13/645,444, filed onOct. 4, 2012, U.S. Application No. 13/645,437, filed on Oct. 4, 2012,U.S. Provisional Application No. 61/543,780, filed on Oct. 5, 2011, andU.S. Provisional Application No. 61/543,714, filed on Oct. 5, 2011, thecontents of which are hereby incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention generally relates to novel curable copolymersformed, at least in part, from tetrafluoropropene. More specifically,the present invention relates to curable copolymers formed in part frommonomeric material comprising 2,3,3,3-tetra-fluoropropene (CF₃CF═CH₂,“HFO-1234yf”) and/or 1,3,3,3-tetrafluoropropene (CH₂═CFCF₃,“HFO-1234ze”), and to compositions and uses thereof

BACKGROUND OF THE INVENTION

Fluoropolymers such as polytetrafluoroethylene (PTFE),polychlorotrifluoro-ethylene (PCTFE) and polyvinylidene fluoride (PVDF)are well known for having excellent thermal, chemical, and weatherresistance, along with favorable properties like water and oilresistance. Unfortunately, the use of such fluoropolymers in coatings isdifficult owing to their poor solubility in industrial solvents—such asxylene and butyl acetate—which are typically used in the coatingindustry. Instead, more exotic solvents must often be used, which notonly affect the economics of a coating, but can also presentenvironmental issues owing to, e.g., potential toxicity of the exoticsolvents.

Accordingly, there is a need to formulate alternative coatings whichhave superior performance properties, yet can use economical industrialsolvents and be environmentally friendly.

Furthermore, polymerization of fluorinated polymers presents a number ofchallenges, e.g., as detailed in prior application Ser. No. 13/645,437(now U.S. Patent Publication No. 2013/0090439 A1), incorporated hereinby reference. Although several types of polymerization methods to maketetrafluoropropene copolymers have been described in prior applicationSer. No. 13/645,437, Applicants have come to further appreciate thatthese polymerization methods have undesirable aspects or limitations,and/or that the polymers produced thereby can be formed with differentand/or improved properties.

Accordingly, Applicants have come to appreciate a need to developimproved processes for making tetrafluoropropene copolymers havingdifferent and/or improved properties for uses in various applications.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a curablefluorocopolymer can be formed by solution copolymerization of themonomers represented by (a), (b) and (c):

(a) 40 to 60 mol % of tetrafluoropropene;

(b) 5 to 45% of vinyl ether or vinyl ester or both of them, representedby formula CH₂═CR1-O(C═O)_(x)R2 and CH₂═CR3-OR4 respectively, wherein R1and R3 is hydrogen or a methyl group, and wherein R2 and R4 is anunsubstituted straight-chain, branched-chain or alicyclic alkyl grouphaving 1 to 12 carbon atoms; and

(c) 3 to 30 mol % of hydroxyalkyl vinyl ether, represented by formulaCH₂═C—R5-OR6, wherein R5 is hydrogen or a methyl group, and R6 is anunsubstituted straight-chain, branched-chain or alicyclic alkyl grouphaving a hydroxyl groups.

In accordance with a second aspect of the present invention, thetetrafluoro-propene is selected from either or both of HFO-1234yf andHFO-1234ze. In accordance with the present invention, the applicantshave found that environmentally friendly HFO-1234yf and HFO-1234ze caneach, and in combination, be employed advantageously as fluorinatedmonomers for the production of polymeric coatings.

In accordance with a third aspect of the present invention, a productcontaining the curable fluorocopolymer has a solvent content of 15-50%,and preferably, 15-25%, so as to provide a concentrated product which iseconomical to ship to the user of the product.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with a preferred embodiment of the present invention, the40-60 mol % tetrafluoropropene in the form of HFO-1234yf and/orHFO-1234ze is used as component (a), and most preferably, 45 to 55 mol%. If a mixture of HFO-1234yf and HFO-1234ze is used, the blending ratioof HFO-1234yf and HFO-1234ze is used can be any ratio, but preferably is0.3 to 0.7: 0.7 to 0.3.

A copolymer in accordance with the present invention may contain vinylether units, vinyl ether units, or a combination thereof as component(b). Preferably, 5 to 45 mol % is used, and most preferably, 25-45 mol %is used. Examples of vinyl ether include alkyl vinyl ethers such asmethyl vinyl ether, ethyl, propyl vinyl ether, n-butyl vinyl ether,isobutyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinylether and lauryl vinyl ether. Vinyl ethers including an alicyclic groupcan also be used, for example, cyclobutyl vinyl ether, cyclopentyl vinylether and cyclohexyl vinyl ether. Examples of vinyl esters include vinylacetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinylcapronate, vinyl laurate, VEOVA-9 (vinyl versatate ester formed from aC9 carbocylic acid, produced by Momentive), VEOVA-10 (vinyl versatateester formed from a C10 carbocylic acid, produced by Momentive) andvinyl cyclohexanecarboxylate.

Examples of the hydroxyalkyl vinyl ether of component (c) includehydroxyl-ethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutylvinyl ether, hydroxypentyl vinyl ether and hydroxyhexyl vinyl ether.Preferably 3 to 30 mol % is used, and most preferably, 5 to 20 mol % isused.

The fluorocopolymer is preferably produced in a solution polymerizationsystem. Examples of solvents for solution polymerization include:esters, such as methyl acetate, ethyl acetate, propyl acetate and butylacetate; ketones, such as acetone, methyl ethyl acetone andcyclohexanone; aliphatic hydrocarbons, such as hexane, cyclohexane,nonane, decane, undecane, dodecane and mineral spirits; aromatichydrocarbons, such as benzene, toluene, xylene, naphthalene, and solventnapthta; alcohols, such as methanol, ethanol, tert-butanol,iso-propanol, ethylene glycol monoalkyl ethers; cyclic ethers, suchtetrahydrofuran, tetrahydropyran, and dioxane; fluorinated solvents,such as HCFC-225 and HCFC-141b; dimethyl sulfoxide; and the mixturesthereof

Preferably, polymerization is conducted in a range of −30° C. to 150° C.depending on the polymerization initiation source and type of thepolymerization medium.

The copolymer of the present invention is preferably prepared bycopolymerizing those monomers and having a number average molecularweight of 5000 to 50000, and more preferably 5000 to 10000. Preferably,the copolymer has a molecular weight distribution of 2 to 10, morepreferably 2.5 to 8, and most preferably 3 to 6. When the number averagemolecular weight is less than 5000, the copolymer is inferior inweatherability and chemical resistance, and when more than 50000, highviscosities may cause operational difficulties.

The copolymer of the present invention has hydroxyl groups and it iscurable with curing agent such as melamine resin curing agent, urearesin curing agent, polybasic acid curing agent and a non-blockedpolyisocyanate curing agent or a blocked polyisocyanate curing agentwhich are used for conventional thermosetting acryl coating. Examples ofmelamine resin curing agents include butylated melamine resin,methylated melamine resin, epoxymelamine resin and the like. Examples ofnon-blocked polyisocyanate 2,4- and 2,6-diisocyanatotoluene (TDI),diphenylmethane-2,4′- and/or -4,4′-diisocyanate (MDI), 1,6-hexamethylenediisocyanate (HDI),1-isocyanato-3,3,5-trimethyl-5-5-isocyanatomethylcyclohexane (IPDI),dicyclohexylmethane diisocyanate (H12MDI), 1,4-diisocyanatobutane,2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane,2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane,1,10-diisocyanato-decane, 1,3- and 1,4-diisocyanatocyclohexane, 1,3- and1,4-bis-(isocyanatomethyl)-cyclohexane,4,4′-diisocyanatodicyclohexylmethane,1-isocyanato-1-methyl-4(3)-isocyanato-methylcyclohexane (IMCI),bis-(isocyanatomethyl)-norbornane, 1,3- and1,4-1,4-bis-(2-isocyanato-prop-2-yl)-benzene (TMXDI),1,5-diisocyanatonaphthalene, 2,4′-, 4,4′-diisocyanatodiphenylmethane,and their dimers, trimers and polymers thereof. As to blockedpolyisocyanate, preferred blocking groups employed for blocking includemetal bisulfite, diethyl malonate (DEM) 3,5-dimethylpyrazole (DMP),methyl-ethylketoxime (MEKO) e-caprolactam (e-CAP), diisopropylamine,dimethyl- pyrazole, methyl ethyl ketoxime (butanone oxime), malonic aciddiethyl ester, secondary amines triazole and pyrazole derivatives. Whenthe curing is conducted at an ordinary by using polyisocyanate, it ispossible to accelerate the curing by an addition of a conventionalcatalyst such as dibutyltin dilaurate

Various solvents can be used for the preparation of solution-type paintsor coatings with the copolymer of the present invention. Preferredsolvents include aromatic hydrocarbons such as xylene and toluene;alcohols such as n-butanol; esters such as butyl acetate; ketones suchas methyl isobutyl ketone, and glycol ethers such as ethyl cellusolveand various commercial thinners. When the copolymer of the presentinvention is used for producing a thermosetting composition for coating,a curing agent such as a melamine type curing agent, a urea type curingagent, a polybasic acid type curing agent, a polyisocyanate type curingagent or the like is simultaneously mixed in the mixing step mentionedabove to produce a one-pack type coating.

On the other hand, when the composition is a normal temperature settingtype coating which uses a polyisocyanate, the curing agent component isseparately prepared to provide a two-pack type coating. In this case,the coating can be cured at room temperature for from several hours toseveral days, and has good properties by controlling the type ofisocyanate and catalyst and their amounts to be added, the concentrationof the copolymer, the contents of the hydroxyalkyl vinyl ether in thecopolymer, and the like.

When the copolymer of the present invention is used as resin for paintor coating, it is possible to form under a mild condition, a film havingexcellent hardness of finish and gloss, flexibility, chemicalresistance, stain resistance and weathering resistance. Such films areuseful not only as a coating for pre-coated galvanized steel, coloredaluminum plate and aluminum frames, but also as an on-site paintablenon-thermally dryable paint. The paint or coating may be used for anumber of substrates, including: metallic substrates; inorganicsubstrates such as glass, cement and concrete; organic substrates, forexample, plastics (such as polyethylene, polypropylene, ethylene-vinylacetate copolymer, nylon, acryl polyester ethylene-polyvinyl alcoholcopolymer, vinyl chloride, vinylidene chloride) and wood materials.Specific applications for the paint or coating include, but are notlimited to, the coating of aluminum swimming pools, the coating ofcolored glass intended for exterior use, and the coating of cement tileused for roofing.

The present invention is further illustrated by the followingnon-limiting examples.

EXAMPLE 1

19.0 g of butyl acetate, 9.5 g of ethyl vinyl ether, 20.8 g of VEOVA-9,8.0 g of hydroxybutyl vinyl ether, and 0.62 g of tert-butylperoxypivalate were charged into a 300 ml stainless steel autoclaveequipped with a stirrer. The mixture was solidified with liquidnitrogen, and deaerated to remove the dissolved air. Then, 50 g of1,3,3,3-tetrafluoro-propene was added to the mixture, and the mixturewas gradually heated to 65° C. in an autoclave. The mixture was stirredfor 18 hours. After the autoclave was cooled to room temperature, theunreacted monomers were purged and the autoclave was opened. Excesssolvent was removed via evaporation.

Yield 92%; Tg (glass transition temperature) of final copolymer=15° C.;Mn=7348; Mw=13789; Mw/Mn=1.87; final polymer concentration=74.7%;viscosity<500 cps.

EXAMPLE 2

20.0 g of butyl acetate, 9.1 g of ethyl vinyl ether, 6.0 g of vinylacetate, 6.7 g of hydroxybutyl vinyl ether, and 0.4 g. of tert-Butylperoxypivalate were charged into a 300 ml stainless steel autoclaveequipped with a stirrer. The mixture was solidified with liquidnitrogen, and deaerated to remove the dissolved air. Then, 40 g of2,3,3,3-tetrafluoro-propene was added to the mixture, and the mixturewas gradually heated to 65° C. in an autoclave. The mixture was stirredfor 18 hours. After the autoclave was cooled to room temperature, theunreacted monomers were purged and the autoclave was opened. Excesssolvent was removed via evaporation.

Yield 91%; Tg of final copolymer=11° C.; Mn=5314; Mw=12646; Mw/Mn=2.38;final polymer concentration=73.8%; viscosity<600 cps.

EXAMPLE 3

20.0 g of butyl acetate, 8.0 g of ethyl vinyl ether, 17.4 g of VEOVA-9,6.7 g. of hydroxybutyl vinyl ether, and 0.63 g. of tert-butylperoxypivalate were charged into a 300 ml stainless steel autoclaveequipped with a stirrer. The mixture was solidified with liquidnitrogen, and deaerated to remove the dissolved air. Then, 60 g of1,3,3,3-tetrafluoro-propene was added to the mixture, and the mixturewas gradually heated to 65° C. in an autoclave. The mixture was stirredfor 18 hours. After the autoclave was cooled to room temperature, theunreacted monomers were purged and the autoclave was opened. Excesssolvent was removed via evaporation.

Yield 93%; Tg of final copolymer=32° C.; Mn=7136; Mw=24103; Mw/Mn=3.37;final polymer concentration=81.1%; viscosity<700 cps.

EXAMPLE 4

20.0 g of butyl acetate, 8.2 g of ethyl vinyl ether, 22.3 g of VEOVA-9,3.4 g of hydroxybutyl vinyl ether, and 0.66 g of tert-butylperoxypivalate were charged into a 300 ml stainless steel autoclaveequipped with a stirrer. The mixture was solidified with liquidnitrogen, and deaerated to remove the dissolved air. Then, 50 g. of1,3,3,3-tetrafluoro-propene was added to the mixture, and the mixturewas gradually heated to 65° C. in an autoclave. The mixture was stirredfor 18 hours. After the autoclave was cooled to room temperature, theunreacted monomers were purged and the autoclave was opened. Excesssolvent was removed via evaporation.

Yield 85%; Tg of final copolymer=12° C.; Mn=4640; Mw=8079; Mw/Mn=1.74;final polymer concentration=78.1%; viscosity<600 cps.

EXAMPLE 5

30.0 g of butyl acetate, 7.6 g of ethyl vinyl ether, 18.4 g of VeoVa-9,6.7 g of hydroxybutyl vinyl ether, and 0.60 g of tert-butylperoxypivalate were charged into a 300 ml stainless steel autoclaveequipped with a stirrer. The mixture was solidified with liquidnitrogen, and deaerated to remove the dissolved air. Then, 60 g of1,3,3,3-tetrafluoro-propene was added to the mixture, and the mixturewas gradually heated to 65° C. in an autoclave. The mixture was stirredfor 18 hours. After the autoclave was cooled to room temperature, theunreacted monomers were purged and the autoclave was opened. Excesssolvent was removed via evaporation.

Yield 82%; Tg of final copolymer=22° C.; Mn=7640; Mw=17620; Mw/Mn=2.31;final polymer concentration=71.7%; viscosity<600 cps.

APPLICATION EXAMPLE

26.1 g of the resulting copolymer was dissolved in 17.9 g of butylacetate, and blended with 22.3 g of titanium oxide. The mixture wasmixed for 1 hour by a paint shaker, then subsequently mixed with 14.8 gof DESMODUR BL4265, and 0.3 g of tin dilaurate (1% concentration). Themixture was then used to coat an aluminum substrate. About 72 hourslater, the physical properties of the surface were tested.

The gloss (ISO 2813) of the surface=70 (20° C.); Hardness (Pencil Test;ASTM D3363)=3H; Flexibility (ASTM D4145)=3T; Adhesion (ASTM D3359)=5B.

From the foregoing, it will be appreciated that although specificexamples have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit orscope of this disclosure. It is therefore intended that the foregoingdetailed description be regarded as illustrative rather than limiting,and that it be understood that it is the following claims, including allequivalents, that are intended to particularly point out and distinctlyclaim the claimed subject matter.

What is claimed is:
 1. A copolymer composition comprising: (a) a firstunit comprising a polymerized monomer selected from the group consistingof 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene; (b) asecond unit comprising a polymerized monomer selected from the groupconsisting of vinyl esters and vinyl ethers; and (c) a third unitcomprising a polymerized monomer comprising a hydroxyl group-containingvinyl ether.
 2. The copolymer composition of claim 1, wherein thecopolymer composition comprises 40 to 60 mol % of said first unit. 3.The copolymer composition of claim 2, wherein the copolymer compositioncomprises 5 to 45 mol % of said second unit, wherein said second unit isselected from the group consisting of alkyl vinyl ethers, vinyl esters,and mixtures thereof
 4. The copolymer composition of claim 3, whereinthe copolymer composition comprises 3 to 30 mol % of said third unit,wherein said second unit consists of hydroxyalkyl vinyl ethers.
 5. Aprocess for the production of the copolymer of claim 1, wherein monomersare polymerized in a solution to produce the copolymer of claim
 1. 6.The process of claim 5, wherein the copolymer has a number averagemolecular weight of between 5000 and
 50000. 7. The process of claim 6,wherein the copolymer has a number average molecular weight of between5000 and
 10000. 8. A composition comprising at least 70 wt % of thecopolymer of claim
 1. 9. The composition of claim 7, wherein thecomposition comprises at least 80 wt % of the copolymer.
 10. Thecomposition of claim 7, wherein the composition comprises 15-25 wt %solvent.
 11. A copolymer composition comprising: (a) a first unitcomprising a polymerized monomer of 2,3,3,3-tetrafluoro-propene; (b) asecond unit comprising a polymerized monomer selected from the groupconsisting of vinyl esters and vinyl ethers; and (c) a third unitcomprising a polymerized monomer comprising a hydroxyl group-containingvinyl ether.
 12. The copolymer composition of claim 11, wherein thecopolymer composition comprises 40 to 60 mol % of said first unit. 13.The copolymer composition of claim 12, wherein the copolymer compositioncomprises 5 to 45 mol % of said second unit, wherein said second unit isselected from the group consisting of alkyl vinyl ethers, vinyl esters,and mixtures thereof
 14. The copolymer composition of claim 13, whereinthe copolymer composition comprises 3 to 30 mol % of said third unit,wherein said second unit consists of hydroxyalkyl vinyl ethers.
 15. Acopolymer composition comprising: (a) a first unit comprising apolymerized monomer of 1,3,3,3-tetrafluoro-propene; (b) a second unitcomprising a polymerized monomer selected from the group consisting ofvinyl esters and vinyl ethers; and (c) a third unit comprising apolymerized monomer comprising a hydroxyl group-containing vinyl ether.16. The copolymer composition of claim 15, wherein the copolymercomposition comprises 40 to 60 mol % of said first unit.
 17. Thecopolymer composition of claim 16, wherein the copolymer compositioncomprises 5 to 45 mol % of said second unit, wherein said second unit isselected from the group consisting of alkyl vinyl ethers, vinyl esters,and mixtures thereof
 18. The copolymer composition of claim 17, whereinthe copolymer composition comprises 3 to 30 mol % of said third unit,wherein said second unit consists of hydroxyalkyl vinyl ethers.